Heat exchangers are commonly used for transferring heat from a very hot gas to a relatively cool gas and/or liquid. Significant temperature differences can exist between those parts of the heat exchanger which are in contact with the hot gas and those parts which are in contact with the cooler gas and/or liquid. These temperature differences can result in differential thermal expansion of the heat exchanger components, which can cause stresses in the joints between the various components and in the components themselves. Over time, these stresses can cause premature failure of joints and/or the heat exchanger components.
In a typical shell and tube heat exchanger, a hot gas stream flowing through the tubes transfers heat to a relatively cool gas and/or liquid flowing through the shell, in contact with the outer surfaces of the tubes. The tubes are much hotter than the surrounding shell, which causes the tubes to expand axially (lengthwise) by a greater amount than the shell. This differential thermal expansion of the tubes and the shell causes potentially damaging stresses on the tube to header joints, as well as on the tubes, the headers, and the shell.
It is known to provide shell and tube heat exchangers with means which allow for differential thermal expansion of the tubes and the shell. For example, commonly assigned U.S. Pat. No. 7,220,392 (Rong et al.) describes a shell and tube fuel conversion reactor in which only one end of the tubes are rigidly connected to the shell through a header. The header at the opposite end is not rigidly connected to the shell, and therefore “floats” in relation to the shell, allowing the tubes to expand freely relative to the shell.
The Rong et al. heat exchanger is typically applied as a fuel reformer in which the floating header is integrated with a cylindrical receptacle for a catalyst. Shell and tube heat exchangers have numerous other applications, and there remains a need to provide solutions for differential thermal expansion in shell and tube heat exchangers for other applications.